Various types of valves are used in the semiconductor industry to control fluid transport and to mix fluids, including highly pure and highly caustic fluids. Although prior valve-manifold combinations effectively provide for the transport and mixing of multiple fluids, they still present certain drawbacks that are not desirable in particular semiconductor applications.
For example, some prior manifolds produce quiescent or dead spots in the primary fluid flow duct which could cause fluids to become stagnant and degrade or could trap solids resulting from fluid contamination. Typically, mixing valves supply secondary fluids by way of an inlet duct flowing into a primary fluid flow duct with the valving located away from the primary fluid flow duct. The duct between the valving and the main flow duct creates such a quiescent or dead spot and can inhibit mixing of the secondary fluid with the primary fluid.
This has been addressed to some extent in the devices disclosed in U.S. Pat. No. 6,192,932. These valve manifolds have a valve with a stem extending through the primary fluid flow duct and a head that seats on a valve seat on the opposite side of the chamber. This arrangement, however, may cause additional potential dead spots in the primary fluid flow duct and disrupts or obstructs the fluid flow by the valve stem extending directly through the middle of the primary fluid flow duct. Such an arrangement may cause excessive pressure drop in the primary duct and subjects large portions of the valve to the primary fluid flow whether the valve is open or closed.
Accordingly, there exists a need in the semiconductor industry for an improved mixing valve manifold assembly and associated methods of eliminating or minimizing dead space and removing or minimizing obstructions that disrupt the main fluid flow duct.